1. Field of the Invention
This invention relates to a shaped, porous extrudate suitable for use in contacting gases and liquids and as a catalyst support. The extrudate has a unique geometric shape which provides a large surface area and a large void fraction and may be impregnated with metals to undertake specific catalytic reactions.
2. Description of the Previously Published Art
To facilitate contacting gases and liquids various types of solid structures have been employed such as tower packings and catalyst particles with hydrotreating catalysts as an example. The tower packings have been made in many shapes such as Rashig rings, Berl saddles, Lessing rings and spiral rings. In general, these are relatively large structures having diameters or lengths on the order of one to several inches. Partition rings sold by The Maurice A. Knight Division of Koch Engineering Company, Inc., are hollow tubular elements with two internal intersecting cross vanes. These rings are made of porcelain or chemical stoneware by a technique which yields zero porosity materials. As a result the particles do not have a large BET nitrogen surface area. In addition, the partition rings are also of a large size with the commercial sizes ranging from 6 inch diameter by 6 inch height down to 3 inch by 3 inch.
Hydrotreating catalysts which are used to contact hydrocarbon liquids with gaseous hydrogen have been made in various shapes. In addition to the conventional spherical shape and the solid tubular extrudate, it has also been known to form extrudates with various external shape configurations. See U.S. Pat. No. 2,408,164 which has various types of shapes and American Cyanamid U.S. Pat. No. 3,966,644 which has a trilobal shape.
A problem with these prior art designs is that if they are made in a small size to increase the geometric surface area, they do not have a sufficiently large void fraction to permit the gas to easily flow through a bed of the particles without a large pressure drop.
3. Objects of the Invention
It is an object of this invention to produce an extrudate structure having a unique shape with a low density, high surface area and with a large void fraction.
It is a further object of this invention to obtain a catalyst support made out of a transitional alumina which permits metals to be directly deposited thereon to form the catalyst and which has a strong crush strength and a coherent geometric shape so that it does not easily break.
It is a further object of this invention to obtain an extrudate structure which is suitable for gas/liquid contacting.
It is also a further object of this invention to obtain a catalyst suitable for use as a hydrotreating catalyst.
These and further objects will become apparent as the description of the invention proceeds.